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外文翻譯 專(zhuān) 業(yè) 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 學(xué) 生 姓 名 蔡 育 鋒 班 級(jí) B材機(jī)022 學(xué) 號(hào) 0210120224 指 導(dǎo) 教 師 陳 杰 來(lái) 文 獻(xiàn) 資 料 專(zhuān) 業(yè) 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 學(xué) 生 姓 名 蔡 育 鋒 班 級(jí) B材機(jī)022 學(xué) 號(hào) 0210120224 指 導(dǎo) 教 師 陳 杰 來(lái) 文 獻(xiàn) 資 料 ［1］ 陳治岸．V帶傳動(dòng)的設(shè)計(jì)．機(jī)械設(shè)計(jì)與制造[C]. 2005年 03期-24. ［2］ 徐金芳. 橡膠運(yùn)輸帶切邊機(jī)生產(chǎn)線設(shè)計(jì)、使用要點(diǎn). 橡膠技術(shù)與裝備. 1996/02-22卷-32. ［3］ 朱銀法. 圓盤(pán)鋸片的加工夾具. 工具技術(shù). 2006/01-第40卷Nal-61. ［4］ 李嵐. 一種自動(dòng)接頭機(jī)的動(dòng)作過(guò)程[A]. 機(jī)械工程與自動(dòng)化. 2006/01第一期. ［5］ 彭少虎. 減速機(jī)、電動(dòng)機(jī)和電子技術(shù)的完美結(jié)合. 現(xiàn)代制造. 2006/01. ［6］ 馬自勤. 數(shù)字組合夾具管理系統(tǒng). 制造技術(shù)與機(jī)床. 2006/03第78-80頁(yè). ［7］ 嚴(yán)慧萍. 復(fù)雜成形刀具的設(shè)計(jì). 制造技術(shù)與機(jī)床. 2006/03第72-73頁(yè). ［8］ 黃青鋒. 基于USB和LabVIEW的數(shù)控切削過(guò)程數(shù)據(jù)采集和分析系統(tǒng)設(shè)計(jì)[B]. 制造業(yè)自動(dòng)化. 2006/01-第28卷第一期46-49頁(yè) ［9］ 胡登恩. 線摩擦多點(diǎn)驅(qū)動(dòng)鋼繩芯帶式輸送機(jī). 礦山機(jī)械. 2006/02-34卷第二期. ［10］夏翔. V帶傳動(dòng)彈性性質(zhì)與承載能力的分析[A]. 江西科學(xué). 2005/06第23卷第6期 鹽城工學(xué)院畢業(yè)設(shè)計(jì)說(shuō)明書(shū) 2006 橡膠成形件自動(dòng)修剪機(jī)夾具及傳動(dòng)部分的設(shè)計(jì) 摘要：隨著橡膠密封圈的大批量生產(chǎn)，對(duì)橡膠成形件自動(dòng)修剪機(jī)的需求也跟著擴(kuò)大。因而對(duì)加工效率提出很高的要求，全自動(dòng)橡膠修剪機(jī)就是為滿(mǎn)足市場(chǎng)需求而設(shè)計(jì)的。本課題是橡膠成形件自動(dòng)修剪機(jī)夾具及傳動(dòng)部分的設(shè)計(jì)，包括機(jī)械手的設(shè)計(jì)，自動(dòng)上料、下料機(jī)構(gòu)設(shè)計(jì)，自動(dòng)切削部分設(shè)計(jì)。在夾具部分設(shè)計(jì)中，分析了兩種方案，一種是采用機(jī)械夾緊方法，另一種是采用氣體負(fù)壓夾緊。考慮多種因素采用了氣體負(fù)壓夾緊。夾具設(shè)計(jì)合理，精度合適。在傳動(dòng)部分，傳動(dòng)方式采用了帶傳動(dòng)，方案結(jié)構(gòu)簡(jiǎn)單，成本低。在機(jī)械手的設(shè)計(jì)過(guò)程中分析到機(jī)械手末端兩種方式，采用了一個(gè)氣爪一個(gè)電磁鐵的方案。在傳感器的設(shè)計(jì)部分中，采用了光電傳感器和電磁式傳感器。本課題設(shè)計(jì)的夾具及傳動(dòng)部分，方案合理，結(jié)構(gòu)緊湊。完成了自動(dòng)修剪機(jī)夾具及傳動(dòng)部分設(shè)計(jì)指標(biāo)要求。設(shè)計(jì)的機(jī)器能夠完成切削范圍：?20—?50，切削效率：15-20個(gè)/分鐘。這種橡膠成形件自動(dòng)修剪機(jī)的大量生產(chǎn)，能夠提高加工效率，增加利潤(rùn)。 關(guān)鍵詞：密封圈；修剪機(jī)；夾具；傳動(dòng) The jig and transmission part designs of rubber forming automatical trimmer machine Abstract：With the mass production of rubber lock ring,the demands of rubber forming automatic trimmer is growing rapidly. High requests are proposed to the processing efficiency , the automatic rubber forming trimmer is designed to satisfy the demands of the market. This topic is about the design of the jig and the transmission part of rubber forming automatic trimmer including the design of mechanic hands, the automatic material loading and discharging parts and design of automatic cutting parts, In the design of jig part,two kind of plans has been analyzed , one is mechanic clamping, the other kind is gas negative pressure clamping . The design of the jig is reasonable, the precision is appropriate. In the transmission part, the belt transmission is adopted ,the structure is simple, the cost is low. The terminal two ways in mechanic hands design process is analyed, a gas fingernail electro-magnet plan is adopted. In the part of sensor design, the electro-optical sensor and the electro-magnetic sensor are adopted. The design of jig and the transmission part is reasonable,the structure is compact. the design target t of the jig and the transmission part of automatic trimmer is attained The machine designed can satisfy the cutting scope: ?20-?50, cutting efficiency: 15-20/Minute, Once this kind of rubber forming automatic cropper is massly produced, it can enhance the processing efficiency of enterprise and the enterprise profit is increased Key words：Lock ring; Trimmer; Jig; Transmission 畢業(yè)設(shè)計(jì)任務(wù)書(shū) 課題：橡膠成形件自動(dòng)修剪機(jī)夾具及傳動(dòng)部分的設(shè)計(jì) 專(zhuān) 業(yè) 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 學(xué) 生 姓 名 蔡 育 鋒 班 級(jí) B材機(jī)022 學(xué) 號(hào) 0210120224 指 導(dǎo) 教 師 陳 杰 來(lái) 專(zhuān) 業(yè) 系 主 任 發(fā) 放 日 期 2006年3月 6 日 一、設(shè)計(jì)內(nèi)容 本設(shè)計(jì)課題主要是根椐一家生產(chǎn)橡膠切邊機(jī)的日資企業(yè)的要求而立的。該課題 的設(shè)計(jì)內(nèi)容包括橡膠成行件自動(dòng)修剪機(jī)自動(dòng)上、下料機(jī)構(gòu)，自動(dòng)切邊機(jī)構(gòu)，自動(dòng)切邊 部分的主軸和夾具部件。主要零部件的零件圖和裝配圖。 二、設(shè)計(jì)依據(jù) 目前由于橡膠密封圈的批量生產(chǎn)，對(duì)切邊機(jī)的要求需求也跟著擴(kuò)大，因而對(duì)機(jī)械 效率提出很高的要求，全自動(dòng)的橡膠切邊機(jī)就是為滿(mǎn)總市場(chǎng)需求而設(shè)計(jì)的。全自動(dòng)的 橡膠切邊設(shè)備會(huì)給企業(yè)帶來(lái)很多方便，提高效率，增加企業(yè)利潤(rùn) 。此設(shè)備在國(guó)內(nèi)有很 大的市場(chǎng)。 三、技術(shù)要求 1、切削速度：2000rpm； 2、切削范圍：?20—?50； 3、切削效率：15-20個(gè)； 4、盡量使用通用件，以便降低制造成本； 四、畢業(yè)設(shè)計(jì)物化成果的具體內(nèi)容及要求 1、設(shè)計(jì)說(shuō)明書(shū)1份，達(dá)1萬(wàn)字以上，且要符合規(guī)范要求； 2、設(shè)計(jì)圖樣全部用AutoCAD繪制，總的繪圖量達(dá)3張A0以上； 3、具體設(shè)計(jì)的圖樣有： （1）夾具裝配圖一張； （2）傳動(dòng)系統(tǒng)裝配圖一張； （3）夾具、傳動(dòng)系統(tǒng)零件圖； 五、畢業(yè)設(shè)計(jì)進(jìn)度計(jì)劃 起訖日期 工作內(nèi)容 備 注 06.03.06—06.03.07 布置任務(wù) 下達(dá)任務(wù)書(shū) 06.03.06—06.03.17 調(diào)查研究，收集資料，熟悉課題,畢業(yè)實(shí)習(xí) 06.03.20—06.03.31 總體設(shè)計(jì)，方案論證 06.04.01—06.05.10 部件、零件設(shè)計(jì)階段 06.05.11—06.06.04 編寫(xiě)說(shuō)明書(shū) 06.06.05—06.06.07 畢業(yè)設(shè)計(jì)預(yù)答辯 06.06.08—06.06.11 修改整理畢業(yè)設(shè)計(jì)材料 06.06.12—06.06.13 材料評(píng)閱 06.06.14—06.06.16 畢業(yè)答辯 06.06.17—06.06.18 材料整理裝袋 六、主要參考文獻(xiàn)： 1、葉偉昌主編.機(jī)械工程及自動(dòng)化簡(jiǎn)明設(shè)計(jì)手冊(cè)(上冊(cè)).北京：機(jī)械工業(yè)出版社，2001 2、葉偉昌主編.機(jī)械工程及自動(dòng)化簡(jiǎn)明設(shè)計(jì)手冊(cè)(下冊(cè)).北京：機(jī)械工業(yè)出版社，2001 3、胡家秀主編.機(jī)械零件設(shè)計(jì)實(shí)用手冊(cè).北京：機(jī)械工業(yè)出版社，1999．10 4、吳宗澤，機(jī)械設(shè)計(jì)課程設(shè)計(jì)手冊(cè)，第二版，高等教育出版社出版，1999 5、液壓與氣壓傳動(dòng),許福玲,陳堯明, 機(jī)械工業(yè)出版社出版,1994 6、邱宣懷，機(jī)械設(shè)計(jì)，第四版，高等教育出版社出版，1997 7、孟憲椅等主編.機(jī)床夾具圖冊(cè).北京：機(jī)械工業(yè)出版社，1991．4 8、成大先,機(jī)械設(shè)計(jì)手冊(cè)，氣壓傳動(dòng)，化學(xué)工業(yè)出版社出版。1989 9、林述溫,機(jī)電裝備設(shè)計(jì),機(jī)械工程出版社,2004 七、其他 4 畢業(yè)設(shè)計(jì) 開(kāi)題論證報(bào)告 專(zhuān) 業(yè) 機(jī)械設(shè)計(jì)制造及自動(dòng)化 學(xué)生姓名 蔡 育 鋒 班 級(jí) B材機(jī)022 學(xué) 號(hào) 0210120224 指導(dǎo)教師 陳 杰 來(lái) 起訖日期 2006 年 3月18 日 課題名稱(chēng)：　橡膠成形件自動(dòng)修剪機(jī)夾具及傳動(dòng)部分的設(shè)計(jì) 一、課題來(lái)源、課題研究的主要內(nèi)容及國(guó)內(nèi)外現(xiàn)狀綜述 主要完成橡膠切邊機(jī)的設(shè)計(jì)。 1）課題來(lái)源：生產(chǎn)實(shí)踐 2）主要內(nèi)容： 目前由于橡膠密封圈的批量生產(chǎn)，對(duì)切邊機(jī)的要求需求也跟著擴(kuò)大，因而對(duì)機(jī)械效率提出很高的要求，全自動(dòng)的橡膠切邊機(jī)就是問(wèn)滿(mǎn)足市場(chǎng)需求而設(shè)計(jì)的。 3）橡膠切邊機(jī)國(guó)內(nèi)產(chǎn)品現(xiàn)狀： 1. YB32系列鋁鑄件金屬制品切邊機(jī)適用于鋁合金金屬制品鑄造行業(yè)，金屬制品的切邊，落料等工藝，設(shè)備分別有廢料落料和成品落料孔。本機(jī)器的工作壓力、行程范圍均可根據(jù)工藝需要進(jìn)行調(diào)整，在壓制后具有自動(dòng)回程動(dòng)作。 2. CY-21-8W真空式萬(wàn)能修邊機(jī)結(jié)構(gòu)簡(jiǎn)單，設(shè)計(jì)先進(jìn)，操作方便，生產(chǎn)效率高，是目前修邊設(shè)備中較先進(jìn)的一種。本機(jī)由機(jī)箱、主軸箱，左右刀架、輸送、傳動(dòng)、電控等部件組成，并設(shè)有光電開(kāi)關(guān)保證操作安全，可單、雙刀垂直、水平、角度切削，也可垂直與水平組合，垂直與角度組合，水平與角度組合，即根據(jù)產(chǎn)品形狀任意調(diào)整。本機(jī)采用進(jìn)口可編程控制器，主軸配置進(jìn)口變頻器，根據(jù)所加工產(chǎn)品直徑大小和線速度的不同，進(jìn)行無(wú)級(jí)變速，便可達(dá)到理想的工藝要求。采用液晶顯示產(chǎn)量，方便直觀；刀架運(yùn)動(dòng)部件采用進(jìn)口軸承，精度高、運(yùn)行可靠；整機(jī)結(jié)構(gòu)合理、精確；體積小，只與電腦桌相仿。氣動(dòng)部件和執(zhí)行部件采用SMC產(chǎn)品，質(zhì)量檔次高，減少維修；采用真空吸附工件，穩(wěn)定、通用性高；本機(jī)人性化設(shè)計(jì)，操作者只需放好工件，便可輕松完成加工過(guò)程，自動(dòng)化程度高，既減輕勞動(dòng)強(qiáng)度又提高生產(chǎn)效率。 本課題擬設(shè)計(jì)的橡膠密封圈切邊機(jī)為高檔橡膠密封圈外徑的精細(xì)修整及內(nèi)唇邊尺寸精確成型設(shè)計(jì)的，該機(jī)廣泛吸收了國(guó)內(nèi)外眾多廠家一些機(jī)型的優(yōu)點(diǎn)，并將它融合于原有機(jī)型中。通過(guò)本機(jī)加工出的工件，具有外觀精細(xì)、 尺寸準(zhǔn)確、同心度極高等優(yōu)點(diǎn)，控制系統(tǒng)采用CMOS數(shù)字邏輯電路，驅(qū)動(dòng)部分采用了無(wú)觸點(diǎn)開(kāi)關(guān)、固態(tài)繼電器和氣動(dòng)邏輯元件，可靠性高，操作簡(jiǎn)便。 二、本課題擬解決的問(wèn)題 此次設(shè)計(jì)主要解決橡膠密封圈的切邊問(wèn)題。 具體安排如下： 1. 全自動(dòng)橡膠切邊機(jī)可行性論證； 2. 刀具方案的設(shè)計(jì)（刀具旋轉(zhuǎn)而工件不轉(zhuǎn)）； 3. 主軸的方案設(shè)計(jì)、夾具的方案設(shè)計(jì)、電機(jī)和帶的選擇及方案設(shè)計(jì)； 4. 上料方案設(shè)計(jì)：機(jī)械手的設(shè)計(jì)。 三、 解決方案及預(yù)期效果 設(shè)計(jì)是橡膠成行件自動(dòng)修剪機(jī)自動(dòng)上、下料機(jī)構(gòu)，自動(dòng)切邊機(jī)構(gòu)，自動(dòng)切邊部分的主軸和夾具部件具有一定的要求。 1． 切削速度：2000rpm ; 2． 切削范圍：∮20-∮50 ； 3． 切削效率：15-20個(gè) ； 4． 盡量使用通用件，以便降低成本。 本次設(shè)計(jì)的產(chǎn)品結(jié)構(gòu)簡(jiǎn)單，設(shè)計(jì)先進(jìn)，操作方便、安全，生產(chǎn)效率高。本機(jī)采用電腦控制，可自動(dòng)、手動(dòng)操作，左右單刀、雙刀同時(shí)、延時(shí)進(jìn)刀均可選擇；刀架移動(dòng)部件采用進(jìn)口軸承，精度高、運(yùn)行可靠；整機(jī)結(jié)構(gòu)合理、精確；體積小 。操作者只要將工件安放在吸盤(pán)上，該裝置就可以自動(dòng)運(yùn)行，輕松的完成切削。 四、課題進(jìn)度安排 3月6日～3月17日．畢業(yè)實(shí)習(xí)階段。 畢業(yè)實(shí)習(xí)，查閱資料，到多個(gè)公司實(shí)踐，撰寫(xiě)實(shí)習(xí)報(bào)告。 3月18日～3月31日．開(kāi)題階段。 提出總體設(shè)計(jì)方案及草圖，填寫(xiě)開(kāi)題報(bào)告。 4月1日～5月10日． 設(shè)計(jì)初稿階段。 完成總體設(shè)計(jì)圖、部件圖、零件圖。 5月11日～6月4日． 中期工作階段。 完善設(shè)計(jì)圖紙，編寫(xiě)畢業(yè)設(shè)計(jì)說(shuō)明書(shū)，中期檢查。 6月5日～6月7日．畢業(yè)設(shè)計(jì)預(yù)答辯。 6月8日～6月13日．畢業(yè)設(shè)計(jì)整改。 圖紙修改、設(shè)計(jì)說(shuō)明書(shū)修改、定稿，材料復(fù)查。 6月14日～6月16日．畢業(yè)答辯。 6月17日～6月18日．材料整理裝袋。 五、指導(dǎo)教師意見(jiàn) 　　 　　　　 　　　　　　　　　 　　 　　年　 月　　日 六、專(zhuān)業(yè)系意見(jiàn) 年　 月　　日 七、學(xué)院意見(jiàn) 年　 月　　日 3 BEM Precision angular contact ball bearing Precision angular contact ball bearing BEM produces special precision angular contact ball bearings for machine tool and other applications where requirements regarding accuracy and speed are very high BEM precision angular contact ball bearings are nonseparable and are essentially single row angular contact ball bearings. In all such bearings the load is transmitted from one raceway to another at an angle to the bearing axis. Therefore carry axial loads acting in one direction in addition to radial loads. Axial forces produced in the bearing when subjected to a radial load must be counteracted by an opposing force applied externally. The bearings are therefore adjusted against a second bearing. The internal design of BEM precision angular contact ball bearings differs appreciably from that of standard single row bearing and reflects the latest state of the art where machine tool bearings are concerned. Only one flange on one ring has reduced height; the contact angles are small, and lightweight one-piece cages with a large number of balls are incorporated. To meet the requirements of modern machine tool applications as fully as possible, BEM precision angular contact ball bearings are made in several series and designs. They can be supplied singly or in matched bearing sets. BEM precision angular contact ball bearings are available in three dimension series-bearing series 719,70 and 72-with a contact angle of 15(designation suffix C)or 25 (designation suffix E). Bearings with the larger contact angle are recommended for applications where high axial stiffness and high axial load carrying capacity are required. The bearings have recently been redesigned as part of the continuous BEM product development program. This has resulted in bearings of C and AC, which have appreciably improved performance. Modified ball/raceway contact conditions, a new outer ring centered cage and more or larger diameter balls have enabled stiffness and load carrying capacity of the bearings to be enhanced, while permitting the bearings to operate an even higher speed. If there is little radial space available, or if very high speeds occur, bearings of series 719 or 70 should be chosen. For heavy loads at relatively moderate speeds then bearings of series 72 are more appropriate. Where stiffness requirements are paramount, bearings of series 719 have the advantage. They also incorporate a large number of balls. Both these factors contribute to a high stiffness of the spindle system: spindle stiffness increases with increasing spindle diameter and bearing stiffness is more strongly influenced by the number than by the size of balls. In Fact the stiffness of these light-series bearing is greater than that of bearings from the heavier series. Preload For single bearings, preload is obtained first after mounting and depends on adjustment against a second bearing which can accommodate axial loads acting in the opposite direction to those acting on the first bearing. Matched sets of two bearings arranged back-to-back of face-to-face are supplied in three preload classes in order to meet different demands in respect of speed, stiffness etc. Class L: light preload Class M: medium preload Class H: heavy preload The degree of actual preload depends on the bearing series, the contact angle and the bearing size. These quoted preloads are nominal values for bearings rranged back-to-back or face-to-face before mounting. Matched sets of three, four or five bearings in tandem/back-to back or tandem/face-to-face arrangements have greater preload than bearing pairs. Preload of mounted bearings When mounted the bearing sets will always have a higher preload. This increase is mainly determined by the fits and the stiffness of the bearing seating on the shaft and in the housing. Cage All BEM precision angular contact ball bearings are fitted with an outer ring centered cage of fabric reinforced phenolic resin. The cages are of a particularly lightweight design in order to keep centrifugal force at a minimum, and are designed to allow free passage of lubricant to the ball/raceway contacts. Designations of precision angular contact ball bearing The complete designation of a single bearing identifies the series, bore diameter, contact angle and design as well as the suffix indicating the tolerance class e. g. 71906 C/P4A. The designations of bearing sets also include suffixes indicating the number of bearings in the set, their arrangement and preload. Limiting speeds The limiting speeds quoted are guideline values and are valid provided that the bearings are lightly loaded (P 0.06C),that they are lightly preloaded by means of springs and that the transport of heat away from the bearing position is good. The values under oil spot lubrication are maximum values and should be reduced for certain other methods of oil lubrication. The values under grease lubrication are maximum values which can be attained using a good quality grease of soft consistency. If matched sets of two, three, four our five bearings are to be used, the limiting speed values given in the tables must be reduced. The appropriate limiting speeds should be multiplied by reduction factors . If the limiting speeds obtained from the above for matched bearing sets are inadequate, a simple design change-the inclusion of intermediate rings between the bearings-will allow appreciable increases to be made. For sets of three bearings, for example, it should then be possible to run at the limiting speeds for paired bearings. Springs to preload the bearings may be beneficial. This type of preload is generally used for high speed operation in order to obtain an even preload over the whole operating range of the machine. Matched bearing sets Depending on requirements, BEM precision angular contact ball bearings may also be supplied as complete sets of two, three, four or five bearings These bearing sets are matched in manufacture so that when the bearings are mounted immediately adjacent to each other, the predetermined value of the preload will be obtained, or the load will be evenly distributed. The bore and outside diameters of bearings belonging to a matched set will not differ by more than half the permissible diameter tolerance The load lines of bearings arranged back-to-back diverge towards the bearing axis. Axial loads can be accommodated in both directions. The back-to-back arrangement is relatively stiff and can also take up tilting moments .The load lines of bearings arranged face-to-face converge towards the bearing axis. Axial loads can be accommodated in both directions. The arrangement is not so stiff as the back-to-back arrangement and is less suitable for tilting moments.In a tandem arrangement, the load lines of the bearings are in parallel. Radial and axial loads are equally distributed over the bearings, but axial loads can only be carried in one direction. A set of bearings in tandem is therefore generally adjusted against another bearing which can take the axial loads acting in the opposite direction. Combinations of tandem and back-to-back or tandem and face-to-face are normally used when the design makes it impossible to adjust a further bearing or bearing set against the tandem set. Selection of bearing type BEM produces several types of high-precision bearings for machine tool and other applications where high demands are placed on accuracy and speed capability. Each of these bearing types has characteristic properties which make it particularly suitable for given applications. When designing a bearing arrangement it is necessary to consider a number of different factors, for example -accuracy, -available space, -loads, -Stiffness, -accommodation of axial displacements, -speed, and -heat generation. Depending on the application, one or other of these factors will have a dominant influence. It is not therefore possible to set down general rules for the selection of bearing type or bearing series. The following remarks should serve to highlight the properties of the different bearing types and to ease bearing selection. Accuracy Running accuracy The running accuracy of a bearing arrangement is governed by the accuracy of all the component parts of the arrangement. Where the bearings are concerned, it is primarily determined by the accuracy of form and position of the raceways on the bearing rings When selecting the appropriate tolerance class for a particular bearing, the maximum radial runout of the inner ring (Kia) is generally the determining factor for most applications Most BEM precision bearings are manufactured to tolerance class P4, SP or P5 specifications. P4 is the standard tolerance class for the angular contact ball bearings, SP the standard for the cylindrical roller bearing and double direction angular contact thrust ball bearings, and P5 the standard class for the taper roller bearings. Normally, the maximum values of Kia given in the table are much higher than the actual values. This means, for example, that if bearings with class SP tolerances are used, running accuracies of under 3 can be achieved. Dimensional accuracy The dimensional accuracy of a bearing is important with respect to the fit between bearing ring and shaft or housing. As the fit influences the clearance or preload of mounted bearings, the tolerances for the bearing and its seatings lie within narrow limits. Where cylindrical roller bearings with a tapered bore are concerned, slightly larger dimensional deviations are permissible than, for example, for angular contact ball bearings with similar running accuracy. This is because the clearance or Preload of the bearing is determined by driving up the inner ring on its tapered seating. Available space Precision bearing arrangements generally call for bearings with a low cross section because of the space available and the high requirements in respect of stiffness and running accuracy of the arrangement. These bearings generally have a large number of rolling elements and consequently have a high stiffness. They also enable relatively large diameter spindles to be used for a given housing bore diameter and therefore exhibit all the advantages which are of importance for both the stiffness and the running accuracy of a bearing arrangement, e.g. spindle bearing arrangementAlmost all of the angular contact ball bearings, cylindrical roller bearings, taper roller bearings and angular contact thrust ball bearings used for machine tool applications belong to the ISO Diameter series 0. It is thus possible, by selecting suitable combinations of bearing, to achieve an optimum bearing arrangement for any particular requirements within the same radial space. For bearing arrangements where less radial space is available, the angular contact ball bearings and cylindrical roller bearings belonging to ISO Diameter Series 9 can be used. Even less radial space is required if bearings belonging to ISO Diameter Series 8 are used. Bearings having the dimensions of this Diameter Series can be supplied on request. Angular contact ball bearings of series 72 belong to the ISO Diameter Series 2 and call for correspondingly larger space. Loads In machine tools-the main application for precision bearings-the load carrying capacity of a bearing is usually of much less importance when determining bearing size than in engineering applications in general. Other criteria such as stiffness, size of the requisite bore in the spindle, machining speeds and accuracy, are the decisive factors. When selecting the bearing type for a given bearing arrangement, however, the magnitude as well as the direction of action of the load do play an important part. As a general rule, roller bearings can carry heavier loads than ball bearings having the same envelope dimensions. Radial loads Cylindrical roller bearings having one ring without flanges, i. e. Some ofl the cylindrical roller bearings shown in this catalogue, can only accommodate purely radial loads. Angular contact ball bearings and Bearings are able to support combined radial and axial loads. Axial loads The double direction angular contact thrust ball bearings are designed to take loads which are purely axial in both directions. For large bearing arrangements, or those subjected to particularly heavy axial loads, single direction thrust ball bearings or cylindrical roller thrust bearings are recommended. They can be supplied with the degree of accuracy required for machine tool applications. Combined loads Combined loads are made up of a radial load and a simultaneously acting axial load. This type of load can be accommodated by bearings having raceways in inner and outer rings, situated at an angle to the bearing axis. Where precision bearings are concerned, the angular contact ball bearings, taper roller bearings fall into category. The ability to carry axial loads is determined by the angle of contact; the larger this is, the greater the axial load which can be accommodated. Stiffness The stiffness of a bearing, which is characterized by the magnitude of its elastic deformation under load, is of particular importance where bearing arrangements are required to have high accuracy. Roller bearings are stiffer than ball bearings because of the contact conditions between the rolling elements and raceways. Stiffness can be enhanced by preloading the bearing. Accommodation of axial displacements Generally a machine component is supported in a locating and a non-locating bearing.